Light emitting device having a plurality of non-polar light emitting cells and a method of fabricating the same

ABSTRACT

The present invention relates to a light emitting device having a plurality of non-polar light emitting cells and a method of fabricating the same. Nitride semiconductor layers are disposed on a Gallium Nitride substrate having an upper surface. The upper surface is a non-polar or semi-polar crystal and forms an intersection angle with respect to a c-plane. The nitride semiconductor layers may be patterned to form light emitting cells separated from one another. When patterning the light emitting cells, the substrate may be partially removed in separation regions between the light emitting cells to form recess regions. The recess regions are filled with an insulating layer, and the substrate is at least partially removed by using the insulating layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/482,851, filed on May 29, 2012, which is a divisional of U.S. Pat.No. 8,211,724 filed on Nov. 23, 2009 and issued on Jul. 3, 2012. Thisapplication, U.S. patent application Ser. No. 13/482,851, and U.S. Pat.No. 8,211,724 claim priority from and the benefit of Korean PatentApplication No. 10-2008-0138238, filed on Dec. 31, 2008. U.S. patentapplication Ser. No. 13/482,851, U.S. Pat. No. 8,211,724, and KoreanPatent Application No. 10-2008-0138238 are hereby incorporated byreference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Exemplary embodiments of the present invention relate to a lightemitting device and a method of fabricating the same, and moreparticularly, to a light emitting device having a plurality of non-polarlight emitting cells and a method of fabricating the same.

2. Discussion of the Background

Gallium Nitride (GaN)-based light emitting diodes (LEDs) are widely usedfor display and backlights. Further, LEDs have less electric powerconsumption and a longer lifespan as compared with conventional lightbulbs or fluorescent lamps. Thus, LEDs have substituted conventionalincandescent bulbs and fluorescent lamps. LED application areas havebeen expanded to the use thereof for general illumination.

In general, a GaN-based nitride semiconductor is grown on aheterogeneous substrate, such as a sapphire or silicon carbidesubstrate. The nitride semiconductor is mainly grown on a c-plane ofsuch a substrate and has piezoelectric properties. A strong polarizationelectric field is generated in an active region of a multiple quantumwell structure due to the piezoelectric properties. Therefore, it isdifficult to increase the thickness of a light emitting layer. Thus,LEDs luminous power may not be significantly improved due to a decreasein light emitting recombination rate.

To prevent the generation of such a polarization electric field, atechnique has recently been studied in which an a-plane nitridesemiconductor is grown by machining GaN crystals grown on a c-planesapphire substrate into a GaN substrate having a crystal face except thec-plane (e.g., an a-plane or m-plane), and using the GaN substrate as agrowth substrate of a nitride semiconductor, or using an m-plane siliconcarbide substrate or r-plane sapphire substrate as the growth substrate.The nitride semiconductor with the a-plane or m-plane has non-polar orsemi-polar properties. Accordingly, it is expected that the nitridesemiconductor has improved is luminous power as compared to a polar LEDhaving a polarization electric field.

LEDs generally emit light by forward current and require supply of DCcurrent. Attempts have been made to develop a technique wherein aplurality of light emitting cells are driven by an AC power source byconnecting the plurality of light emitting cells in reverse parallel orusing a bridge rectifier, and LEDs fabricated by this technique havebeen commercialized. Further, an LED has been developed which can emithigh-output and high-efficiency light by a high-voltage DC power sourceby forming a plurality of light emitting cells on a single substrate andconnecting them in series.

To use a LED connected to a high-voltage AC or DC power source using aplurality of light emitting cells, the plurality of light emitting cellsare electrically separated from one another and are connected throughwires. Since a conventional sapphire substrate is an insulativesubstrate, the plurality of light emitting cells can be electricallyisolated from one another when using a nitride semiconductor grown onthe sapphire substrate. However, since a GaN substrate generally hascharacteristics of an n-type semiconductor, when a plurality of lightemitting cells are fabricated using non-polar or semi-polar nitridesemiconductor layers grown on the GaN substrate, there is a problem inthat the light emitting cells may be electrically connected by the GaNsubstrate.

To solve such a problem, nitride semiconductor layers may be grown on aGaN substrate, and the GaN substrate may then be separated from thenitride semiconductor layers. Conventionally, nitride semiconductorlayers are grown on a sapphire substrate, and the sapphire substrate isthen separated from the nitride semiconductor layers using a laserlift-off process. However, since the GaN substrate and the nitridesemiconductor layers grown thereon have similar physical and chemicalproperties, it is difficult to separate the nitride semiconductor islayers from the GaN substrate.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide a light emittingdevice having a plurality of non-polar light emitting cells and a methodof fabricating the same.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

Exemplary embodiments of the present invention disclose a method offabricating a light emitting device having a plurality of non-polarlight emitting cells. The method includes forming a substrate having anupper surface. The upper surface is a non-polar crystal face or asemi-polar crystal face. The upper surface forms an intersection anglewith respect to a c-plane. The method includes disposing nitridesemiconductor layers on the substrate, and patterning the nitridesemiconductor layers to form light emitting cells separated from oneanother. The patterning includes partially removing the substrate inseparation regions between the light emitting cells to form recessregions. The method further includes disposing an insulating layer tofill the recess regions, and removing, at least partially, the substrateso that the insulating layer is exposed.

Exemplary embodiments of the present invention disclose a light emittingdevice including a substrate, a plurality of non-polar or semi-polarlight emitting cells, material layers, an insulating layer, at least onewire, and an interlayer insulating layer. The plurality of non-polar orsemi-polar light emitting cells are formed on the substrate and spacedapart from one another. Each of the light emitting cells includes afirst conductive-type upper semiconductor layer, an active layer, and asecond conductive-type lower semiconductor layer. The material layerscover the first conductive-type upper semiconductor layer of the lightemitting cells. The insulating layer is disposed on the light emittingcells and fills spaces between the material layers. The at least onewire electrically connects the light emitting cells under the insulatinglayer. The interlayer insulating layer covers the at least one wires.The interlayer insulating layer is interposed between the substrate andthe light emitting cells.

Exemplary embodiments of the present invention disclose a light emittingdevice having a plurality of non-polar light emitting cells. The lightemitting device includes a substrate, a plurality of non-polar lightemitting cells, electrodes, an insulating layer, and at least one wire.The plurality of non-polar light emitting cells is spaced apart from oneanother on the substrate. Each of the light emitting cells includes afirst conductive-type upper semiconductor layer, an active layer, and asecond conductive-type lower semiconductor layer. The electrodes areformed on the light emitting cells. The electrodes are electricallyconnected to the second conductive-type lower semiconductor layer of oneof the light emitting cells and extending towards another light emittingcell adjacent to the one of the light emitting cells. The insulatinglayer fills spaces between the light emitting cells above theelectrodes. The insulating layer has at least one opening for exposingthe electrodes. The at least one wire connects the light emitting cells.The at least one wire has one end electrically connected to the firstconductive-type upper semiconductor layer of the one of the lightemitting cells and another end of the at least one wire beingelectrically connected to the electrode electrically connected to thesecond conductive-type lower semiconductor layer of the adjacent lightemitting cell through the at least one opening of the insulating layer.

It is to be understood that both the foregoing general description andthe is following detailed description are exemplary and explanatory andare intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theprinciples of the invention.

FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are sectionalviews illustrating a method of fabricating a light emitting devicehaving a plurality of non-polar light emitting cells according toexemplary embodiments of the present invention.

FIG. 8, FIG. 9, and FIG. 10 are sectional views illustrating a method offabricating a light emitting device having a plurality of non-polarlight emitting cells according to exemplary embodiments of the presentinvention.

FIG. 11, FIG. 12, FIG. 13, FIG. 14, and FIG. 15 are sectional viewsillustrating a method of fabricating a light emitting device having aplurality of non-polar light emitting cells according to exemplaryembodiments of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which exemplary embodiments of the inventionare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these exemplary embodiments is areprovided so that this disclosure is thorough, and will fully convey thescope of the invention to those skilled in the art. In the drawings, thesize and relative sizes of layers and regions may be exaggerated forclarity. Like reference numerals in the drawings denote like elements.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or directly connected to the other element or layer, orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on” or “directly connected to”another element or layer, there are no intervening elements or layerspresent.

“Non-polar” light emitting cell may refer to a light emitting cellformed of a nitride semiconductor in which a polarization electric fieldis not induced by a piezoelectric field. A “semi-polar” light emittingcell may refer to a light emitting cell formed of a nitridesemiconductor having a polarization electric field relatively smallerthan that of a nitride semiconductor having a c-plane as a growth plane.As long as not specifically mentioned hereinafter, the term “non-polar”includes the term “semi-polar.”

Hereinafter, exemplary embodiments of the present invention aredescribed in detail with reference to the accompanying drawings.

FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are sectionalviews illustrating a method of forming a plurality of non-polar lightemitting cells according to exemplary embodiments of the presentinvention.

Referring to FIG. 1, nitride semiconductor layers 25, 27 and 29 may begrown on a substrate 21. The substrate 21 may be a GaN single crystalsubstrate, and an upper surface of the substrate 21 may be a crystalface that forms an intersection angle with respect to a c-plane. Theupper surface of the substrate 21 may be, for example, an a-plane, anm-plane, or an r-plane. However, the upper surface of the substrate isnot particularly limited, and may be another crystal face.

The substrate 21 may be prepared by separating a GaN single crystal,which may be grown on a c-plane sapphire substrate by a hydride vaporphase epitaxy (HVPE), from the sapphire substrate and then cutting theGaN single crystal along a crystal face that forms an intersection anglewith respect to a c-plane. Alternatively, the substrate 21 may beprepared by growing a GaN layer on an r-plane sapphire substrate orm-plane silicon carbide substrate, and subsequently separating the GaNlayer from the sapphire or silicon carbide substrate. The substrate 21may be an a-plane GaN substrate.

The nitride semiconductor layers 25, 27 and 29 may include a firstconductive-type semiconductor layer 25, an active layer 27, and a secondconductive-type semiconductor layer 29. Each of the nitridesemiconductor layers 25, 27 and 29 may be formed to have a single- ormulti-layered structure. Particularly, the active layer 27 may be formedto have a multiple quantum well structure.

Before growing the first conductive-type nitride semiconductor layer 25,a nucleation layer and/or a buffer layer (not shown) formed of a nitridematerial first may be grown on the substrate 21. The buffer layer may begrown as a GaN-based material layer or GaN. The buffer layer may beformed to facilitate growth of the nitride semiconductor layers 25, 27and 29, and may be an undoped layer or an impurity-doped layer.

The first conductive-type semiconductor layer 25, the active layer 27,and the second conductive-type semiconductor layer 29 may be formed of aIII-N compound semiconductor and grown by a process such as metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy(MBE). The nitride semiconductor layers may be grown along the growthface of the GaN substrate 21. Accordingly, the nitride semiconductorlayers may be grown as non-polar nitride semiconductors along the growthface of the GaN substrate 21.

The first and second conductive types may be n- and p-types or p- andn-types, respectively. For example, in some cases, the first conductivetype may be an n-type semiconductor, and the second conductive type maybe a p-type semiconductor.

Referring to FIG. 2, the nitride semiconductor layers 25, 27, and 29including the first conductive-type semiconductor layer 25, the activelayer 27, and the second conductive-type semiconductor layer 29, may bepatterned to form a plurality of light emitting cells 30. Each lightemitting cell 30 may include a first conductive-type semiconductor layer25, a second conductive-type semiconductor layer 29 positioned on oneregion of the first conductive-type semiconductor layer 25, and anactive layer 27 interposed between the first conductive-typesemiconductor layer 25 and the second conductive-type semiconductorlayer 29. Each light emitting cell 30 may be formed by partiallyremoving the second conductive-type semiconductor layer 29 and theactive layer 27, such that a portion of the first conductive-typesemiconductor layer 25 may be exposed.

While forming the light emitting cells 30, the substrate 21 may bepartially etched in separation regions, thereby forming recess regions21 a. The recess regions 21 a may be formed in a stripe shape to bespaced apart from one another, or in a mesh shape to be connected to oneanother.

Referring to FIG. 3, an insulating layer 31 may be disposed to fill therecess regions 21 a. The insulating layer 31 may be filled in theregions between the light emitting cells 30 such that top surfaces ofthe insulating layer 31 may be slightly below upper surfaces of thefirst conductive-type semiconductor layers 25. The insulating layer 31may be formed of an insulating material, such as spin on glass (SOG),silicon oxide, and silicon nitride. The insulating layer 31 may beformed by applying or depositing an insulating material on the lightemitting cells 30 and then partially removing the insulating material sothat the upper surfaces of the first conductive-type semiconductorlayers 25 are exposed.

Referring to FIG. 4, a side insulating layer 33 for covering sides ofthe light emitting cells 30 may be formed on the insulating layer 31.The side insulating layer 33 may have openings through which upperportions of the light emitting cells 30 are exposed and also hasopenings through which the upper surfaces of the first conductive-typesemiconductor layers 25 are exposed.

A reflective layer 35 may be formed on each of the light emitting cells30 (e.g., on each of the second conductive-type semiconductor layers29). The reflective layer 35 may be formed of, for example, Silver (Ag)or Aluminum (Al). Further, a protective metal layer 37 may be formed tocover the reflective layer 35. The protective metal layer 37 may coverthe reflective layer 35 to prevent diffusion and oxidation of thereflective layer 35. The protective metal layer 37 may be formed to havea single- or multi-layered structure. For example, the protective metallayer may be formed of Nickel (Ni), Titanium (Ti), Tantalum (Ta),Platinum (Pt), Tungsten (W), Chromium (Cr), or Palladium (Pd).

Thereafter, wires 39 may be formed to electrically connect the lightemitting cells 30. The wires 39 may connect the first conductive-typesemiconductor layer 25 and second conductive-type semiconductor layer 29of adjacent light emitting cells such that the light emitting cells 30are connected in series. A wire 39 may connect the protective metallayer 37 and the first conductive-type semiconductor layer 25, and maybe electrically connected to the second conductive-type semiconductorlayer 29 through the protective metal layer 37 and the reflective layer35. The reflective layer 35 and/or the protective metal layer 37 may beomitted, and the wire 39 may be directly connected to the secondconductive-type semiconductor layer 29.

Referring to FIG. 5, after the wires 39 are formed, an interlayerinsulating layer 41 may be formed to cover the light emitting cells 30.The interlayer insulating layer 41 may prevent the light emitting cells30 from being short-circuited to one another.

A second substrate 51 may be bonded to the interlayer insulating layer41. The second substrate 51 may be formed of a material having a thermalexpansion coefficient similar to that of the GaN substrate 21. Thesecond substrate 51 may be formed by forming a bonding metal 43 on theinterlayer insulating layer 41, forming a bonding metal 45 on the secondsubstrate 51, and then bonding the bonding metals 43 and 45 to eachother.

Referring to FIG. 6, after the second substrate 51 is bonded to theinterlayer insulating layer 41, the GaN substrate 21 may be removed, atleast partially. The GaN substrate 21 may be removed by a polishing oretching process. At this time, the insulating layer 31 filled in therecess regions are exposed.

The GaN substrate 21 has physical-chemical properties similar to thoseof the nitride semiconductor layers (e.g., 25, 27, and 29) grownthereon. In conventional art, it is difficult to separate the GaNsubstrate 21 from the nitride semiconductor layer. However, according toexemplary embodiments of the present invention, an interface between theGaN substrate 21 and the nitride semiconductor layers can be easilydistinguished by the insulating layer 31. Accordingly, an end point maybe easily determined in the polishing or etching process, so that theGaN substrate 21 can be partially or completely removed.

When the GaN substrate 21 is partially removed, the first nitridesemiconductor layers 25 may still cover residual portions of the GaNsubstrate 21. If the GaN substrate 21 is completely removed, a bufferlayer (not shown) may be coupled to the first nitride semiconductorlayers 25, or the first nitride semiconductor layers 25 may be exposed.

Referring to FIG. 7, after the GaN substrate 21 is removed, roughenedsurfaces R may be formed on the residual portions of the GaN substrate21 (or the buffer layer) or the first nitride semiconductor layers 25.The roughened surface R may be formed using any suitable means,including, for example, photoelectrochemical (PEC) etching.

Accordingly, a light emitting device having a plurality of non-polarlight emitting cells 30 spaced apart from one another on the secondsubstrate 51 may be manufactured according to the method describedabove. The light emitting device comprises light emitting cells 30connected in series by the wires 39, whereby the light emitting devicecan be driven by a high-voltage DC power source. Alternatively, a lightemitting device may comprise a plurality of arrays connected in seriesby the wires 39. These arrays may be connected in reverse parallel, sothat the light emitting device can be driven by a high-voltage AC powersource.

FIG. 8, FIG. 9, and FIG. 10 are sectional views illustrating a method offabricating a light emitting device having a plurality of non-polarlight emitting cells according to exemplary embodiments of the presentinvention.

Referring to FIG. 8, after the light emitting cells 30 are formed, aninsulating layer 71 for covering the light emitting cells 30 may beformed. The insulating layer 71 may fill the recess regions 21 a and maycover sides of the light emitting cells 30. The insulating layer 71 mayhave openings exposing portions of the first conductive-typesemiconductor layers 25 and the second conductive-type semiconductorlayers 29.

The insulating layer 71 may be formed by filling insulating material inthe recess regions 21 a, covering the light emitting cells 30, and thenpatterning the insulating material. Alternatively, the insulating layer71 may be formed by filling insulating material in the recess regions 21a, and then forming a side insulating layer (not shown) for coveringsides of the light emitting cells 30.

A reflective layer 73 and a protective metal layer 75 may be formed onthe second conductive-type semiconductor layer 29. The opening on thefirst conductive-type semiconductor layer 25 may be filled with ametallic material 75 a. The metallic material 75 a may be the samematerial used for the protective metal layer 75.

Referring to FIG. 9, bonding metals 77 may be formed to electricallyconnect the first conductive-type semiconductor layer 25 of one of thelight emitting cells 30 to the second conductive-type semiconductorlayer 29 of another adjacent light emitting cell 30. The bonding metals77 may be spaced apart from one another to connect the light emittingcells 30 in series. The bonding metals 77 may be formed on theinsulating layer 71 to electrically connect the metallic materialsformed in the openings of the insulating layer 71. Alternatively, thebonding metals 77 may electrically connect the first conductive-typesemiconductor layers 25 to the second conductive-type semiconductorlayers 29 through the openings.

Bonding metals 79 may be formed on a second substrate 81. The bondingmetals 79 may be formed on and bonded to the bonding metals 77,respectively.

Referring to FIG. 10, the substrate 21 may be removed, at leastpartially, as described with reference to FIG. 6. After a portion of thesubstrate 21 is removed, roughened surfaces may be formed on residualportions of the substrate 21 (or the buffer layer) or the first nitridesemiconductor layers 25.

In FIG. 8, FIG. 9, and FIG. 10, a light emitting device having lightemitting cells 30 electrically connected by bonding metals 77 isdescribed. The light emitting device may be driven by a high-voltage DCor AC power source depending on the electrical connection of the bondingmetals 77.

FIG. 11, FIG. 12, FIG. 13, FIG. 14, and FIG. 15 are sectional viewsillustrating a method of fabricating a light emitting device having aplurality of non-polar light emitting cells according to exemplaryembodiments of the present invention.

Referring to FIG. 11, after the nitride semiconductor layers 25, 27, and29 of FIG. 1 are formed, light emitting cells 90 separated from oneanother may be formed by patterning the nitride semiconductor layers 25,27, and 29. Each of the light emitting cells 90 comprises a firstconductive-type semiconductor layer 25, a second conductive-typesemiconductor layer 29 formed on the first conductive-type semiconductorlayer 25, and an active layer 27 interposed between the firstconductive-type semiconductor layer 25 and the second conductive-typesemiconductor layer 29. The first conductive-type semiconductor layer 25and second conductive-type semiconductor layer 29 may have the samewidth and area as shown in FIG. 11.

Before growing the nitride semiconductor layers 25, 27, and 29 on a GaNgrowth substrate 21, a nucleation layer and/or a buffer layer 23 formedof a nitride material may be first grown on the GaN growth substrate 21.The buffer layer 23 may also be separated into plural regions whilepatterning the nitride semiconductor layers 25, 27, and 29.

While forming the light emitting cells 30, the substrate 21 may bepartially etched in separation regions formed by removing the nitridesemiconductor layers 25, 27, and 29, thereby forming recess regions. Therecess regions may be formed in a stripe shape to be spaced apart fromone another or in a mesh shape to be connected to one another. When thebuffer layer 23 is relatively thick, the recess regions may be definedin the buffer layer 23.

Subsequently, an insulating layer 91 may fill the recess regions. Theinsulating layer 91 may fill regions between the light emitting cells90. Upper surfaces of the light emitting cells 90 may be exposed. Theinsulating layer 91 may be formed of an insulating material, such asSOG, silicon oxide, or silicon nitride. The insulating layer 91 may beformed by applying or depositing an insulating material on the lightemitting cells 90 and partially removing the insulating material so thatthe upper surfaces of the second conductive-type semiconductor layers 29are exposed. Alternatively, after forming an insulating layer 91 to befilled in the recess regions, a side insulating layer may be formed tocover sides of the light emitting cells 90.

Electrodes E may be formed on the exposed second conductive-typesemiconductor layers 29. Each of the electrodes E may be electricallyconnected to the second conductive-type semiconductor layer 29 of onelight emitting cell 90 and may extend towards an adjacent light emittingcell 90. Each electrode E may comprise a reflective layer 93 formed onthe second conductive-type semiconductor layer 29 and a protective metallayer 95 for covering the reflective layer 93. The protective metallayer 95 may extend towards an adjacent light emitting cell 90. Theprotective metal layer 95 may be extended and disposed on the insulatinglayer 91. The electrodes E may be spaced apart from one another.

Referring to FIG. 12, an interlayer insulating layer 101 may be formedon the electrodes E. The interlayer insulating layer 101 may cover theelectrodes E and may fill gaps between the electrodes E. The interlayerinsulating layer may be formed of any suitable material, including, forexample, a silicon oxide layer or a silicon nitride layer.

A bonding metal 103 may be formed on the interlayer insulating layer101, and a bonding metal 105 may be formed on a second substrate 111.The bonding metal 103 may be formed of a mixture of Gold (Au) and Tin(Sn), for example, in an 80/20 AuSn weight percentage %). The secondsubstrate 111 may be a substrate having a thermal expansion coefficientidentical to that of the substrate 21.

The bonding metals 103 and 105 may be bonded to face each other, so thatthe second substrate 111 may be bonded to the interlayer insulatinglayer 101.

Referring to FIG. 13, the substrate 21 may be removed, at leastpartially, as described with reference to FIG. 6. After a portion of thesubstrate 21 is removed, a GaN-based material layer (e.g., residualportions of the growth substrate 21), the buffer layer 23, or the firstconductive-type semiconductor layers 25 may be exposed. The insulatinglayer 91 filled in the recess regions may also be exposed.

Referring to FIG. 14, openings 91 a may be formed by patterning theexposed insulating layer 91 and may expose the electrodes E. Inparticular, the openings 91 a allow the electrodes E (e.g., theprotective metal layers 95) extending toward adjacent light emittingcells to be exposed. Further, openings 92 a may be formed by patterningportions of the residual portions of the substrate 21 and the bufferlayer 23 covering the first conductive-type semiconductor 25. Theopenings 92 a may expose the first conductive-type semiconductor layers25.

Referring to FIG. 15, wires 113 may be formed to electrically connectthe light emitting cells 90. Each of the wires 113 may have one endelectrically connected to the first conductive-type semiconductor layer25 of one of the light emitting cells 90 (e.g., the upper semiconductorlayer 25 in FIG. 15), and the other end electrically connected to thesecond conductive-type semiconductor layer 29 of an adjacent lightemitting cell 90 (e.g., the electrode E electrically connected to thelower semiconductor layer 29 in FIG. 15). The residual portions of thesubstrate 21 and the buffer layer 23 may remain on the firstconductive-type semiconductor layers 25 of the light emitting cells 90.One end of each wire 113 may be electrically connected to the firstconductive-type semiconductor layer 25 through the opening 92 a.

A serial array of light emitting cells 90 or at least two serial arraysof light emitting cells 90 may be formed on the substrate 111 by thewires 113. Accordingly, a light emitting device driven by a high-voltageDC or AC power source is described herein above. Alternatively, a serialarray of light emitting cells 90 may be formed on the substrate 111 bythe wires 113 and connected to a bridge rectifier formed on thesubstrate 111, whereby the light emitting cells 90 can be driven by anAC power source. The bridge rectifier may also be formed by connectingthe light emitting cells 90 by the wires 113.

Before or after forming the wires 113, roughened surfaces R may beformed on GaN-based material layers for covering the firstconductive-type semiconductor layers 25 (e.g., on the residual portionsof the substrate 21 and the buffer layer 23). When the firstconductive-type semiconductor layers 25 are exposed, roughened surfacesR may be formed on the first conductive-type semiconductor layers 25.

Before forming the wires 113, pads (not shown) may be formed on thefirst conductive-type semiconductor layers 25 and/or the electrodes E toimprove the adhesion or ohmic contact property of the wires 113.

According to exemplary embodiments of the present invention, a lightemitting device having a plurality of non-polar light emitting cells isprovided. A GaN substrate may be used as a growth substrate. Further,while separating light emitting cells, the exposure of a metal may beprevented, thereby preventing the generation of metallic etchingbyproducts and oxidation or etching damage of a reflective layer.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A light emitting diode, comprising: a substrate; an interlayerinsulating layer disposed on the substrate; a first nitridesemiconductor stacked structure disposed on the interlayer insulatinglayer, the first nitride semiconductor stacked structure comprising afirst conductive-type semiconductor layer, an active layer, and a secondconductive-type semiconductor layer; a second nitride semiconductorstacked structure disposed on the interlayer insulating layer, thesecond nitride semiconductor stacked structure comprising a firstconductive-type semiconductor layer, an active layer, and a secondconductive-type semiconductor layer; at least one wire electricallyconnected to the first nitride semiconductor stacked structure and thesecond nitride semiconductor stacked structure; a side insulating layercovering at least partial side surfaces of the first nitridesemiconductor stacked structure and the second nitride semiconductorstacked structure, the side insulating layer configured to separate theside surfaces of the first and second nitride semiconductor stackedstructure from the wire, wherein the second nitride semiconductorstacked structure is electrically connected to the first nitridesemiconductor stacked structure by the wire in reverse parallel.
 2. Thelight emitting diode of claim 1, wherein a top surface of the firstnitride semiconductor stacked structure is a light extraction surface,and the top surface of the first nitride semiconductor stacked structurecomprises a roughened surface.
 3. The light emitting diode of claim 2,wherein: the first nitride semiconductor stacked structure furthercomprises a material layer; the roughened surface is formed on a surfaceof the material layer, and the material layer is formed of thehomogeneous material with a growth substrate; and semiconductor layersof the first nitride semiconductor stacked structure are grown on thegrowth substrate.
 4. The light emitting diode of claim 2, wherein: thefirst nitride semiconductor stacked structure further comprises residualportions of a growth substrate; and the roughened surface is formed onone surface of the residual portions of the growth substrate.
 5. Thelight emitting diode of claim 4, wherein the growth substrate comprisesa GaN substrate.
 6. The light emitting diode of claim 2, whereinsemiconductor layers of the first nitride semiconductor stackedstructure, the second nitride semiconductor stacked structure, or boththe first nitride semiconductor stacked structure and the second nitridesemiconductor stacked structure are non-polar or semi-polarnitride-based semiconductor layers.
 7. The light emitting diode of claim6, further comprising an insulating layer disposed between the firstnitride semiconductor stacked structure and the second nitridesemiconductor stacked structure.
 8. The light emitting diode of claim 7,further comprising a bonding metal interposed between the substrate andthe interlayer insulating layer.
 9. The light emitting diode of claim 8,further comprising a reflective layer interposed between the interlayerinsulating layer and the first nitride semiconductor stacked structure.10. The light emitting diode of claim 9, further comprising a protectivemetal layer covering the reflective layer.
 11. The light emitting diodeof claim 10, wherein a top surface of the insulating layer is atapproximately the same height as the light extraction surface.
 12. Thelight emitting diode of claim 11, wherein the side insulating layer ispartially interposed between the first nitride semiconductor stackedstructure and the interlayer insulating layer, and between the secondnitride semiconductor stacked structure and the interlayer insulatinglayer
 13. The light emitting diode of claim 1, wherein semiconductorlayers of the first nitride semiconductor stacked structure and thesecond nitride semiconductor stacked structure comprise nitride-basedsemiconductor layers, and the nitride-based semiconductor layers have agrowth plane other than a c-plane.